Use of mixtures of organofunctionally modified polysiloxanes with branched alcohols in the production of flexible polyurethane foams

ABSTRACT

The invention relates to the use of mixtures of organofunctionally modified polysiloxanes with branched alcohols in the production of flexible polyurethane foams.

RELATED APPLICATIONS

This application claim priority to German application No. 100 59 057.8,filed Nov. 28, 2000, herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to the use of mixtures of organofunctionallymodified polysiloxanes with branched alcohols in the production offlexible polyurethane foams.

2. Description of Related Art

Polysiloxane-polyoxyalkylene block copolymers, hereinafter referred toas polyether siloxanes, are used in the production of polyurethanefoams. They make it possible to obtain a uniform, fine pore structureand stabilize the foam during the production process.

However, depending on the production process and depending on whatfurther raw materials are used, an unsatisfactory cell structure isobtained in some cases. For example, the use of polyols having a highpolypropylene oxide content frequently tends to give a coarser cellstructure.

The equipment used can also lead to an irregular or coarse cellstructure, for example when using low-pressure mixing heads or when theraw materials are simply mixed by stirring at atmospheric pressure.

The use of alternative blowing agents, in particular CO₂, also placesparticularly high demands on the polyether siloxane in respect ofachieving a fine-pored cell structure. Owing to the advantageousecological balance, this liquid CO₂ technology has become increasinglyimportant in the past years. In this process, pressurized CO₂ is used asblowing gas in addition to the CO₂ formed by chemical reaction of theisocyanates used with water. This technology is described, for example,in EP-A-0 645 226. However, the introduction of this technology hasshown that the spontaneous foaming of the pressurized CO₂ on dischargeof the reaction mixture places increased demands on the cell formationcharacteristics of the components used in the foam formulation. This canalso be explained by the isocyanate/water reaction, which previouslycommenced slowly over a period of several seconds, leading only to slowsaturation of the liquid phase with gas and thus the slow formation ofgas bubbles, viz. the cream phase of the foam.

This previously slow process which forms the basis for the morphologicalproperties, i.e. cell count and cell size distribution of the resultingfoam is now compressed into fractions of a second, namely the timerequired by the raw materials to pass from the pressurized mixing beadof a foaming machine and the adjoining discharge device to the ambientpressures of one atmosphere. This results, in a manner similar toshaving foam from a spray can, to spontaneous formation of a foam due tovaporization of liquid CO₂. The defects which occurred in such foamswere nonuniform, sometimes enlarged cells within the foam structure, andthe use of suitable foam stabilizers can be useful for minimizing thesedefects. Nevertheless, there is often the problem, depending on boundaryconditions (pressure, raw material temperatures, use of solids in theformulation), of stabilizers which are well-suited according to thepresent state of the art, e.g. as described in U.S. Pat No. 5,357,018 orU.S. Pat. No. 5,321,051, not producing fully defect-free foams.

In principle, the cell structure can be made finer by increasing theamount of polyether siloxane used, but there is limited latitude forachieving this increase, firstly because of the accompanying phenomenonof overstabilization which then occurs and can lead to a high proportionof closed cells, in extreme cases even to shrinkage of the foam, andsecondly because of the associated unfavorable economics.

In principle, the use of additives to polyether siloxanes or flexiblefoam formulations for increasing the fineness of the cells is alreadyknown.

EP-A-0 900 811 describes the use of cyclic carbonates as agents forincreasing the fineness of the cells in flexible foam formulations.However, the cyclic carbonates are effective only in amounts of the sameorder of magnitude as the polyether siloxane and additionally have thedisadvantage of being volatile components which vaporize from thefinished foam.

EP-A-0 976 781 described the combined use of polyether siloxanes andsalts of organic acids. The cells become finer even at lowconcentrations, but the solubility of the salts is relatively limited sothat the use of water as cosolvent becomes necessary. The use of suchcombinations is therefore restricted to hydrolysis-stable polyethersiloxanes. Furthermore, water contributes to the blowing reaction withisocyanates and may, depending on the concentration used, have to betaken into account in the formulation calculation.

U.S. Pat. No. 4,520,160 describes a process for preparing polyethersiloxanes in the presence of fatty alcohols. The latter prevent gelformation during the preparation. The resulting products are preferablyused as emulsifiers in cosmetic applications. The document also mentionsthe in-principle possibility, documented by means of an example, of usein polyurethane foams, but liquid CO₂ applications are not mentioned.The use of the product described has, according to this document, nonegative influence on the applications mentioned. On the basis of theinformation provided, the experiment described using a mixture of apolyether siloxane having an SiC structure and isostearyl alcohol givesan open-celled foam whose properties are equal to or better than a foamresulting from a comparative experiment in which isopropyl alcohol isused in place of isostearyl alcohol. Specific criteria for theassessment are not mentioned. In particular, no information on cellstructure is given. The foam is only described by the characterization“good foam”. Analysis of the example leaves the question of which classof polyurethane compounds is being addressed largely open, since, forexample, the polyol type is not defined. The catalyst employed is theorganotin compound dibutyltin dilaurate (DBTDL) which could indicate anHR slabstock application. DBTDL is frequently used in flexible foamapplications exclusively in HR slabstock and not in conventionalslabstock; the latter application requires tin octoate as catalyst.DBTDL is additionally employed in the production of rigid foams and alsoof elastomers/shoe soles, or classes of polyurethane different fromflexible foams.

Our attempts to repeat the example lead not to a flexible foam but to aprepolymer-like elastomer without foam character. The use of a definedamount of water and amine catalysts would be absolutely necessary forproducing a flexible foam.

Neither water nor amine catalyst are mentioned in the example; theproduct is thus not a flexible foam. The foam parameters described forthe products of the experiment, e.g. foam height and air permeability,are thus not comprehensible.

The present invention relates to formulations for producing flexiblepolyurethane foams, by which are meant both conventional flexiblepolyether foams and flexible polyether foams produced with the aid ofliquid CO₂ technology.

Conventional flexible polyether foams are produced using as catalyst,apart from a tertiary amine, at least one of the following:

a) a metal salt of an organic acid, for example an alkali metal,alkaline earth metal, Al, Sn, Pb, Mn, Co, Bi or Cu salt of an organicacid such as octanoic acid, ricinoleic acid, acetic acid, oleic acid,lauric acid or hexanoic acid;

b) alkoxides and phenoxides of various metals, e.g. Ti(OR)₄, Sn(OR)₄,Sn(OR)₂, Al(OR)₃, where R are alkyl or aryl radicals;

c) chelate complexes of various metals with acetylacetone,benzoylacetone, trifluoroacetylacetone, ethyl acetoacetate,salicylaldehyde, cyclopentanone-2-carboxylate, acetylacetonimine,bisacetylacetone alkylenimines, salicylaldimine and the like, withpossible metals being Be, Mg, Zn, Cd, Pb, Ti, Zr, Sn, As, Bi, Cr, Mo,Mn, Fe, Co, Ni or ions such as MoO₂ ⁺⁺ and UO₂ ⁺⁺ and the like;

d) acidic metal salts of strong acids, e.g. iron chloride, tin chloride,antimony trichloride and bismuth chloride or nitrate.

The polyols suitable for flexible foams are usually polyether polyols asare described, for example, in U.S. Pat. No. 3,346,557 and polymerpolyols as are described, for example, in U.S.-Re-28,715 and U.S. Pat.No. 3,346,557, U.S. Pat. No. 3,823,201, U.S. Pat. No. 3,850,861, U.S.Pat. No. 4,454,255, U.S. Pat. No. 4,458,038, U.S. Pat. No. 4,50,194,U.S. Pat. No. 4,390,645 and also U.S. Pat. No. 4,431,754. The polyolswhich are preferably employed are trifunctional and have predominantlysecondary OH groups.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide, inter alia,improved stabilizer systems in the production of flexible polyurethanefoams.

DESCRIPTION OF THE INVENTION

It has surprisingly been found that synergistically acting mixtures ofpolyether siloxanes with small amounts (from 0.1 to about 30%,preferably from about 5 to about 10%,. based on the polyether siloxanes)of branched fatty alcohols and derivatives thereof have a significantlymore effective influence on reducing the size of the cells than do thepolyether siloxanes alone. The simultaneous use of the constituents ofthe mixture is of critical importance. Separate introduction of thebranched fatty alcohol, for example via the polyol component, does notlead to the desired effect. The mixtures claimed may further comprisesolvents such as a monool, diol or triol of a polyether, a glycol havinga low molecular weight or a nonionic surfactant. The solvents themselveshave no influence on the surface-active properties of the polyethersiloxane in the flexible foam formulation per se, but represent amaterial which is chemically reactive in the polyurethane formulationand may be present in the mixture claimed.

Polyether Siloxanes:

The polyether siloxanes on which the present invention is based arepolysiloxane-polyoxyalkylene copolymers comprising modifiedpolyoxyalkylene building blocks.

The invention, in principle, relates to all structures which can be usedgenerally in the production of flexible polyurethane foams. However, animportant factor for the synergistic action of the two components of themixture is the use of a polyether siloxane which preferably has acertain nucleating action, i.e. gives a satisfactory cell structure evenwhen used alone. In contrast, polyether siloxanes which when used alonegive a coarse cell structure frequently do not allow production ofsynergistically active mixtures in the sense of the invention.

For example, hydrophobic stabilizers are particularly suitable forachieving a fine cell structure, while on the other hand hydrophilicrepresentatives lead, as a result of their structure, to a rather coarsecell when employed alone or in a mixture with the alcohol used accordingto the invention.

The polyoxyalkylene block can be linked to the polysiloxane via ahydrolysis-stable SiC bond or via a less hydrolysis-stable SiOC bond.

The number of siloxane units in the polysiloxane and the number ofpossible linkages with the polyoxyalkylene can be altered in virtuallyany desired way.

Polysiloxane-polyoxyalkylene block copolymers are described in numerouspublications.

For example, DE -A-15 70 647 describes SiOC-linked polyether siloxanes.The preparation of this class of polyether siloxanes is described in,for example, DE-A-10 12 602, DE-A-10 40 251, DE-A-11 20 147and U.S. Pat.No. 3,115,512.

The preparation of SiC-linked polysiloxane-polyoxyalkylene blockcopolymers is described, for example, in U.S. Pat. No. 2,846,458 and inDE-A-12 20 615 and DE-A-11 53 166.

The polyether siloxanes used in the present invention have the formulaI,

where the radicals

R¹ are alkyl radicals or aryl radicals,

R² are R¹ and/or R³ and/or R⁴,

R³ is a polyether radical of the formula II

—(Y)_(e)[O(C2H_(4−d)R′_(d)O)_(m)(C_(x)H_(2x)O)_(p)Z]_(w)  (II)

 with the proviso that

e=0 to 1,

w=to 4,

d=1 to 3,

m≧1,

x=2 to 4, whereby x is 2, 3 and/or 4 in the same polyether radical;i.e., x is such that a polyether radical may contain C₂H₄O—, C₃H₆O— andC4H₈O units either individually or in combination, and

p≧1, and

Y is a (w+1)-valent hydrocarbon radical which may be branched,

R′ is selected from the group consisting of monovalent, aliphatic oraromatic hydrocarbon radicals preferably having from 3 to 18 carbonatoms,

Z is hydrogen or a monovalent organic radical including an acyl radical,the sum m+p=1 to 150,

R⁴ is a polyether radical of the formula III

—(F)_(f)[O(C_(x)H_(2x)O)_(r)Z]_(g)  (III)

 with the proviso that

f=0 or 1,

x=2 to 4,

g=1 to 4 and

r≧1,

F is a (g+1)-valent hydrocarbon radical which may be branched,

a is from 1 to 100 when b is from 6 to 8,

a is from 1 to 200 when b is from 3 to 6,

a is from 1 to 300 when b is from 0 to 3,

b 0 to 8.

For the purposes of the present invention, particular preference isgiven to using polysiloxanes of the formula I in which the indices eand/or f=0. These are accordingly SiOC structures.

For the purposes of the present invention, particular preference isgiven to using polyether siloxanes of the formula I in which R² in atleast one case is R³, with the proviso that m>p.

Alternatively, preference is in the same way given to usingpolysiloxanes of the formula I in which the indices e and f=1. These areaccordingly SiC structures.

The alcohols and derivatives thereof on which the invention is based arecompounds of the formula IV

R—CH₂—O—R′  (IV)

where

R=a branched alkyl radical having at least 7 carbon atoms and preferablyup to 26 carbon atoms and

R′=H, acyl or R³ as defined above.

The branched alcohols and derivatives of the formula IV used in thepresent invention have an alkyl chain R of at least 8 carbon atoms, withthe proviso that the chain has at least one branching point.

The alcohols and derivatives used do not have to have surfactantcharacter in order to achieve the effect produced according to theinvention.

Examples of compounds claimed are the commercially available Guerbet andZiegler alcohols and also naturally branched oxo and isotridecylalcohols.

For the purposes of the present invention, particular preference isgiven to using the mixture of polysiloxane of the formula I and branchedalcohol in the production of flexible polyurethane foams comprisingliquid carbon dioxide as blowing agent.

For the purposes of the present invention, particular preference isgiven to using the mixtures of polysiloxane of the formula I andbranched alcohol and derivatives thereof of the formula IV in an amountof from about 0.3 to about 3%, based on the flexible polyurethane foamformulation.

The present invention further provides mixtures of organofunctionalmodified polysiloxanes of the formula I

where the radicals

R¹ are alkyl radicals or aryl radicals,

R² are R¹ and/or R³ and/or R⁴,

R³ is a polyether radical of the formula II

—(Y)_(e)[O(C2H_(4−d)R′_(d)O)_(m)(C_(x)H_(2x)O)_(p)Z]_(w)  (II)

 with the proviso that

e=0 to 1,

w=1 to 4,

d=1 to 3,

m≧1,

x=2 to 4, whereby x is 2, 3 and/or 4 in the same polyether radical;i.e., x is such that a polyether radical may contain C₂H₄O—, C₃H₆O— andC₄H₈O units either individually or in combination, and

p≧1, and

Y is a (w+1)-valent hydrocarbon radical which may be branched,

R′ is selected from the group consisting of monovalent, aliphatic oraromatic hydrocarbon radicals, preferably having from 3 to 18 carbonatoms,

Z is hydrogen or a monovalent organic radical including an acyl radical,the sum m+p=1 to 150,

R⁴ is a polyether radical of the formula III

—(F)_(f)[O(C_(x)H_(2x)O)_(r)Z]_(g)  (III)

 with the proviso that

f=0 or 1,

x=2 to 4,

g=1 to 4and

r≧1,

F is a (g+1)-valent hydrocarbon radical which also may be branched,

a is from 1 to 100 when b is from 6 to 8,

a is from 1 to 200 when b is from 3 to 6,

a is from 1 to 300 when b is from 0 to 3,

b=0 to 8,

with the proviso that at least one of the indices e and/or f=0, andbranched alcohols and derivatives thereof of the formula IV

R—CH₂—O—R′  (IV)

 where

R=a branched alkyl radical, preferably having from 7 to 26 carbon atomsand

R′=H, acyl or R³ as defined above.

EXAMPLES

A flexible polyurethane foam was produced in an open wooden box havingdimensions of 27×27 cm and a wall height of 27 cm by foaming apolyurethane formulation comprising the following constituents:

100 parts of a trifunctional polypropylene glycol having an OH number of56 (Desmophen® 7186)

4.05 parts of water

0.15 part of Tegoamin®DMEA

0.05 part of N-ethylmorpholine

0.2 part of tin octoate

3.0 parts of a physical blowing agent (dichloromethane)

and a 1.12 molar amount, based on hydroxyl groups present in theformulation, of isocyanate groups in the form of the commerciallyavailable 80:20 mixture of the 2,4- and 2,6-isomers of tolylenediisocyanate designated as T 80.

As foam-stabilizing agent, a silicone polyether copolymer of the tradename Tegostab B 8123 which is obtainable by hydrosilylation of siloxanescontaining Si-H groups with allyl-initiated polyethers and correspondsto an SiC-polyether siloxane as described in U.S. Pat. No. 5,321,051 forstabilizing the resulting foams was used. In the examples according tothe invention, this stabilizer was blended with small amounts of abranched fatty alcohol, while in the comparative experiments which arenot according to the invention the pure product or the mixture withblending components was used or the branched alcohol was not blendedwith the stabilizer but added separately to the formulation, for exampleto the polyol. After curing of the foam, the foam body obtained was cuthorizontally and the cell structure found on the cut surface at a heightof 15 cm above the bottom of the foam was evaluated. Evaluation criteriawere the number of cells/cm and the regularity of the cell structureobtained. In addition, the backpressure produced when 8 liters perminute are passed through the foam sample via a circular feed linehaving a diameter of 2 cm was determined as a measure of the open cellcontent of the foams obtained. The lower the backpressure measured, themore open-celled is the foam obtained.

The following results were obtained:

Concentration of Tegostab Additive Additive Cell fineness B 81231/amount 2/amount Cell [number of Back-pressure Ex. [parts] [parts][parts] structure cells per cm] [mm of water] Comp. 1 0.38 none —slightly  6 33 irregular Comp. 2 0.38 dipropylene — Slightly  7 23glycol/0.22 irregular Comp. 3 0.38 dipropylene isostearyl Slightly 6-715 glycol/0.22 alcohol irregular separately added 0.06 Comp. 4 0.38dipropylene Propylene slightly 10 17 glycol/0.16 carbonate/0.06irregular Ex. 1 0.38 dipropylene isostearyl regular 14 21 glycol/0.16alcohol/0.06 Ex. 2 0.38 dipropylene isododecyl regular 13-14 19glycol/0.16 alcohol/0.06

It can clearly be seen that the use of branched alcohols as component ofa flexible foam stabilizer has a surprisingly positive effect on thecell fineness and regularity of the polyurethane foams obtained. Thiseffect could also be demonstrated in machine tests using liquid,pressurized CO₂ as blowing agent (corresponding to the CarDio®,Novaflex™ or Beamech™ process).

In these tests, a formulation analogous to the above example was foamedwith 4.8 parts of water and 2 parts of CO₂ on a Novaflex™ unit. Asstabilizer, a highly active stabilizer as disclosed in EP-A-0 585 771was used. In the example according to the invention, isostearyl alcoholwas used as component in the stabilizer. In the comparative example, theisostearyl alcohol was replaced by dipropylene glycol. The cellstructure of the foam was subsequently assessed and assigned anevaluation on the scale defect-free, slightly defective, moderatelydefective, defective or highly defective.

Composition of the stabilizer mixture Cell structure 0.9 part ofTegostab B 8123 + moderately defective 0.5 part of dipropylene glycol0.9 part of Tegostab B 8123 + defect-free 0.4 part of dipropyleneglycol + 0.1 part of isostearyl alcohol

It can be seen that the effect of an improvement in the cell finenesswhen using a branched alcohol also occurs under the conditions offoaming by means of liquid CO₂ as blowing agent.

The above description of the invention is intending to be illustrativeand not limiting. Various changes or modifications in the embodimentsdescribed may occur to those skilled in the art. These changes can bemade without departing from the scope or spirit of the invention.

What is claimed is:
 1. A process for producing flexible polyurethanefoams which comprises reacting a polyol and an isocyanate in thepresence of water, optionally a blowing agent and a mixture comprising:i) at least one organofunctionally modified polysiloxane of the formulaI,

 where the radicals R¹ are alkyl radicals or aryl radicals, R² are R¹and/or R³ and/or R⁴, R³ is a polyether radical of the formula II—(Y)_(e)[O(C₂H_(4−d)R′_(d)O)_(m)(C_(x)H_(2x)O)_(p)Z]_(w)  (II)  with theproviso that e=0 to 1, w=1 to 4 d=1 to 3, m≧1, x=2 to 4, whereby x maybe 2, 3, or 4 in the same polyether radical, and p≧1, and Y is a (w+1)-valent hydrocarbon radical which may be branched, R′ is selected fromthe group consisting of monovalent, aliphatic and aromatic hydrocarbonradicals Z is hydrogen or a monovalent organic radical, the sum m+p=1 to150, R⁴ is a polyether radical of the formula III—(F)_(f)[O(C_(x)H_(2x)O)_(r)Z]_(g)  (III)  with the proviso that f=0 or1, x=2to 4, g=1 to 4and r≧1, F is a (g+1) -valent hydrocarbon radicalwhich may be branched, a is from 1 to 100 when b is from 6 to 8, a isfrom 1 to 200 when b is from 3 to 6, a is from 1 to 300 when b is from 0to 3, b=0 to 8 and ii) at least one branched alcohol and derivativesthereof of the formula R—CH₂—O—R′  (IV)  where R=a branched alkylradical having at least 7 carbon atoms and R′=H, acyl or R³ as definedabove.
 2. The process according to claim 1, wherein the mixturecomprises i) at least one organofunctionally modified polysiloxane ofthe formula I where the radicals R¹ are alkyl radicals or aryl radicals,R² are R¹ and/or R³ and/or R⁴, R³ is a polyether radical of the formulaII —(Y)_(e)[O(C₂H_(4−d)R′_(d)O)_(m)(C_(x)H₂x_(O))_(p)Z]_(w)  (II)  withthe proviso that e=0 to 1, w=1 to 4, d=1 to 3 m≧1, x=2 to 4, whereby xis 2, 3 and/or 4 in the same polyether radical p≧1, and Y is a(w+1)-valent hydrocarbon radical which may be branched, R′ is selectedfrom the group consisting of monovalent, aliphatic and aromatichydrocarbon radicals, each having from 3 to 18 carbon atoms, Z ishydrogen or a monovalent organic radical, the sum m+p=1 to 150, R⁴ is apolyether radical of the formula III—(F)_(f)[O(C_(x)H_(2x)O)_(r)Z]_(g)  (III)  with the proviso that f=0 or1, x=2 to 4, g=1 to 4 and r≧1, F is a (g+1)-valent hydrocarbon radicalwhich may be branched, a is from 1 to 100 when b is from 6 to 8, a isfrom 1 to 200 when b is from 3 to 6, a is from 1 to 300 when b is from 0to 3, b=0 to 8, ii) compounds of the formula IV R—CH₂—O—R′  (IV).
 3. Theprocess as claimed in claim 1, wherein e and/or f in the polysiloxane ofthe formula I is
 0. 4. The process as claimed in claim 1, wherein e andf in the polysiloxane of the formula I is
 1. 5. The process as claimedin claim 4, wherein R² in at least one case is R³ in the polyethersiloxane of the formula I, with the proviso that m>p.
 6. The process asclaimed in claim 1, which comprises blowing agent.
 7. The process asclaimed in claim 1, wherein branched alcohol is a Guerbet or Ziegleralcohol.
 8. The process according to claim 1, wherein the alcohol is abranched oxo or isotridicyl alcohol.
 9. The process as claimed in claim1, wherein the alcohol and derivatives thereof of the formula IV ispresent in an amount of from about 0.1 to about 30% by weight, based onthe amount of polysiloxanes of the formula I.
 10. The process as claimedin claim 1, wherein the mixture comprising the polysiloxane and branchedalcohol is present in an amount of from about 0.3 to about 3%, based onthe flexible polyurethane foam formulation.
 11. The process as claimedin claim 6, wherein the blowing agent is pressurized carbon dioxide. 12.A process for producing flexible polyurethane foams which comprisesreacting a polyol and an isocyanate in the presence of a catalyst,optionally a blowing agent, and a mixture comprising: i) at least oneorganofunctionally modified polysiloxane of the formula I,

 where the radicals R¹ are alkyl radicals or aryl radicals, R² are R¹and/or R³ and/or R⁴, R³ is a polyether radical of the formula II —(Y)_(e)[O(C₂H_(4−d)R′_(d)O)_(m)(C_(x)H_(2x)O)_(p)Z]_(w)  (II)  withthe proviso that e=0 to 1, w=1 to 4, d=1 to 3, m≧1, x=2 to 4, whereby xmay be 2, 3, or 4 in the same polyether radical, and p≧1, and Y is a(w+1) -valent hydrocarbon radical which may be branched, R′ is selectedfrom the group consisting of monovalent, aliphatic and aromatichydrocarbon radicals Z is hydrogen or a monovalent organic radical, thesum m+p=1 to 150, R⁴ is a polyether radical of the formula III—(F)_(f)[O(C_(x)H_(2x)O)_(r)Z]_(g)  (III)  with the proviso that f=0 or1, x=2to 4, g=1 to 4 and r≧1, F is a (g+1) -valent hydrocarbon radicalwhich may be branched, a is from 1 to 100 when b is from 6 to 8, a isfrom 1 to 200 when b is from 3 to 6, a is from 1 to 300 when b is from0to 3, b=0 to 8 and ii) at least one branched alcohol and derivativesthereof of the formula R—CH₂—O—R′  (IV)  where R=a branched alkylradical having at least 7 carbon atoms and R′=H, acyl or R³ as definedabove; wherein the catalyst is at least one compound selected from thegroup consisting of a metal salt of an organic acid, an alkoxide orphenoxide of a metal, a chelate complex of a metal, and an acidic metalsalt of a strong acid.
 13. The process according to claim 12, whereinthe a metal salt of an organic acid is an alkali metal, alkaline earthMetal, or an Al, Sn, Pb, Mn, Co, Bi or Cu salt of an organic acidselected from the group consisting of octanoic acid, ricinoleic acid,acetic acid, oleic acid, lauric acid and hexanoic acid; the alkoxide orphenoxide of a metal is Ti(OR)₄, Sn(OR)₄, Sn(OR)₂, or Al(OR)₃, where Rare alkyl or aryl radicals; the chelate complex of a metal is thechelate of a complex metal with acetylacetone, benzoylacetone,trifluoroacetylacetone, ethyl acetoacetate, salicylaldehyde,cyclopentanone-2-carboxylate, acetylacetonimine, bisacetylacetonealkylenimines, salicylaldimine where the metal is Be, Mg, Zn, Cd, Pb,Ti, Zr, Sn, As, Bi, Cr, Mo, Mn, Fe, Co, or Ni or ions selected from thegroup consisting of MoO₂ ⁺⁺ and UO₂ ⁺⁺; the acidic metal salt of strongacids is iron chloride, tin chloride, antimony trichloride, bismuthchloride or bismuth nitrate.